Monday, February 22, 2016

Some
traits of cities seem universal, shared by all cities, large and small, past
and present. Neighborhood organization is one of these urban universals,
something I have talked about in previous posts (here, and here, for example). See Smith et al. (2015). Other traits seem more limited to only
some kinds of cities, or cities in only a few regions or periods. For example, Inka
cities were full of standardized stone storage facilities, built and maintained
by the state (Figure 1); such storehouses are rare in other cities. Contemporary
cities have organized trash pick-up (whether government or privately run),
while past cities lacked this institution. One of my reasons for writing this
blog is to explore the nature of these similarities and differences among
cities across the span of deep history and around the globe.

A
number of lines of research now suggest that that the role of cities as “social
reactors” may be another urban universal. This means that the presence of
greater numbers of people—in larger settlements—leads to more social
interactions, which in turn produces social and economic benefits far beyond
what smaller settlements can produce. Cities are places where individuals
interact socially in all kinds of ways. As the number of people in a city goes
up, the number of potential interactions with other people also rises, but it rises
much faster than the number of people. The increase is exponential (Figure 2). These interactions have been called "buzz" (Storper and Venables 2004).

Fig 2. Interactions & pop.

A
long line of research in the social sciences focuses on the negative consequences
of growing city size. More people means more crowding, and crowding in cities
can cause stress, both psychological and social. Larger cities have more crime
and more poverty. Social relations may be less personal in larger cities, with
neighbors less willing to help one another. One intriguing theory, by
archaeologist Roland Fletcher (1995),
posits thresholds of population size and density that growing settlements
cannot cross unless they develop new means of communication and social
integration (Figure 3). Otherwise the stresses of living with too many people
make life intolerable and settlements will disintegrate or break down.When early village dwellers figured out how
to communicate information with writing, and how to divide their settlements into
increasingly specialized spaces and buildings, they could achieve the transition
to the first cities, which had more people and denser populations.

Fig. 3. Fletcher's book

Growing
city size also has its positive consequences. In early times, the most basic attraction
of city life was protection. War and violence have been prominent in all eras
of history. Once our ancestors adopted agriculture and settled down, the
concept of property was born. Property and riches led to crime and warfare.
People quickly figured out that there was strength in numbers. Kings and rulers
in past times wanted their subjects to move into town. People were easier to
tax and control in cities, and their economic activity created growth and
prosperity that benefitted the rulers.

Now let's jump to the present. In
contemporary cities, urban growth has what economists call “agglomeration
effects” (Figure 4). This means that as firms and factories set up in cities,
they attract workers and create greater specialization and increased
productivity. These in turn generate growth, attracting even more people to
cities and creating more output. The spatial concentration of people and firms in
cities leads to economies of scale, which pushes urban productivity even
higher. Knowledge and skills can be transferred among people, and from one industry
to another, because of their concentration in a city.

Figure 4. Agglomeration effects

This
picture of agglomeration economies is a pretty standard view of contemporary
cities, as seen by urban economists and economic urban geographers. It is easy
to see how cities in this sense can be called “social reactors.” They are
places where concentrations of people, firms, and institutions create wealth
and growth, built on a foundation of the way the people interact with one
another. This is definitely the way cities operate within modern capitalist
economies. But what about cities before the modern era, before the birth of
capitalism? They didn’t have wage labor; workers did not move among firms and
industries as they do today; land markets were rudimentary or non-existent; and
economies were far less dynamic than they are today.

Were
cities in the past also “social reactors”? My answer to this question a few
years ago would have been “no.” It seemed to me (and to many urban scholars)
that the generative properties of cities—their capacity to grow quickly and
expand economically, their ability to create wealth—arose from the capitalist
economy. Ancient cities did not have agglomeration economies, and thus their
roles as social reactors must have been far less important than today.

But
then I started working on urban scaling with three colleagues. The results have
been surprising and illuminating to me, and important for a general
understanding of urbanism. I’ve blogged a bit about the scaling work previously (an early post, and later), and I will talk about it more in the future. For now, I
will say that this research had convinced me that the concept of social
reactors definitely applies to ancient cities, and it even applies to large
villages and towns. Something fundamental happens when people live together in
settlements, and these fundamental processes become stronger as a settlement
gets bigger.

Here
is a very brief description of three reasons why I changed my mind on ancient
cities and settlements as social reactors.

First,
the very regular patterns of how urban traits change with city population, as found
for contemporary cities, also apply to past cities. These relationships are
analyzed with scaling models, and our research group has found that the scaling
patterns of modern cities are also present in cities before the modern era.

Fig. 5. Mandan village

Second,
these scaling relationships are also found in village settlements among tribal
peoples (Figure 5). To me, this is an astounding finding. Generative processes
that are thought to be “urban” in nature also affect much smaller settlements
in societies that lack cities, kings, laws, and social classes. Wow, this is
nothing short of incredible.

Third,
the explanation for the above reasons comes from Luis Bettencourt’s (2013) formal model of scaling. Rather than
tracing the city dynamics that create scaling to agglomeration economies, this
model traces them to face-to-face social interaction within a structured built
environment. This means that they should be present in historical cities, in
ancient cities, and in non-urban village settlements. And they are!

After
a few years of working groups and meetings our project now has a name: “The
Social Reactors Project: Human Settlement and Networks in History” and a
website. We are physicist Luis Bettencourt, economist Jose Lobo, archaeologist
Scott Ortman, and me. Our website has just gone live this week! Check it out for our work and papers, and for
the names of postdocs and students who are helping.

The idea
that face-to-face social interactions (buzz) are crucial to cities and to urban life
is nothing new. Here are three quotes from diverse authors:

“The central theme of this book is that
cities magnify humanity’s strengths. Our social species’ greatest talent is the
ability to learn from each other, and we learn more deeply and thoroughly when
we’re face-to-face.”

--Urban economist Edward Glaeser (2011:250).

“Again and again, we find that one key to
creating social capital is to build in redundancy of contact. … Common spaces
for commonplace encounters are prerequisites for common conversations and
common debate.”

The innovation
of our scaling research group is to demonstrate, with solid quantitative data,
that these face-to-face interactions were not only present and important in the
past, but that they also generated change and output in the past, just as they
do today. We have a bunch of papers in production and in press, and some published (see the website). The role of cities as social reactors is not just a contemporary
phenomenon, an attribute of capitalist economies. Rather, it is a fundamental
attribute of human settlements through deep history and across space.

About Me

I am an archaeologist who works on Aztec sites and Teotihuacan.I do comparative and transdisciplinary research on cities, and also households, empires, and city-states. I view my discipline, archaeology, as a Comparative Historical Social Science.
My home pageMy papers to downloadMy page on Academia.edu
Twitter: @MichaelESmith
I am Professor in the School of Human Evolution & Social Change at Arizona State University; Affiliated Faculty in the School of Geographical Science and Urban Planning; Fellow, ASU-SFI Center for Biosocial Complex Systems; Core Faculty in the Center for Social Dynamics Complexity. Also, I have an affiliation with the Colegio Mexiquense in Toluca, Mexico.